diff --git a/config.h.in b/config.h.in
index f6755a1d..95514fdd 100644
--- a/config.h.in
+++ b/config.h.in
@@ -39,6 +39,9 @@
 /* Dynamic library loading is supported */
 #undef HAVE_DLOPEN
 
+/* __int128_t is supported */
+#undef HAVE_INT128
+
 /* Define to 1 if you have the <inttypes.h> header file. */
 #undef HAVE_INTTYPES_H
 
diff --git a/configure b/configure
index 93a4302e..73e52030 100755
--- a/configure
+++ b/configure
@@ -4742,6 +4742,9 @@ ac_fn_cxx_check_type "$LINENO" "__int128_t" "ac_cv_type___int128_t" "$ac_include
 if test "x$ac_cv_type___int128_t" = xyes; then :
   HAVE_INT128=yes
 
+
+$as_echo "#define HAVE_INT128 1" >>confdefs.h
+
 fi
 
 
diff --git a/configure.ac b/configure.ac
index 1b46578b..701bd994 100644
--- a/configure.ac
+++ b/configure.ac
@@ -85,7 +85,9 @@ AC_HEADER_STDC
 # Checks for type
 #-------------------------------------------------------------------------
 
-AC_CHECK_TYPE([__int128_t], AC_SUBST([HAVE_INT128],[yes]))
+AC_CHECK_TYPE([__int128_t],
+              [AC_SUBST([HAVE_INT128],[yes])
+              AC_DEFINE([HAVE_INT128], [1], [__int128_t is supported])])
 
 #-------------------------------------------------------------------------
 # Default compiler flags